The hard disk drive has been a staple of data storage networks for some time. In the last two decades, the cost of hard disk drives has steadily decreased while the density of data stored on these drives has increased significantly, yielding cheaper and higher capacity storage devices. Solid state storage devices have also become increasingly popular, especially in portable devices, owing to certain performance benefits. For example, the lack of moving parts in solid state drives allows data read times to be relatively constant across the device. In addition, there is no physical read-head bottleneck in solid state drives. Conversely, the physical movement of actuators, read/write heads, and platters in hard disk drives can result in access times for a single block of data that can be on the order of a few milliseconds to tens of milliseconds in many instances. As such, hard disk drives can create bottlenecks in modern input/output (I/O) systems.
The bottlenecks associated with hard disk drives have motivated the development of numerous I/O latency reduction algorithms for such drives. These algorithms include, for example, read-ahead algorithms and more complex variants thereof. Typically, these algorithms rely on scheduling schemes that predict and exploit common access patterns. However, such algorithms are failing to keep up with growing demands for I/O access speed increases.
There is a general need for techniques that are capable of reducing average access times in hard disk drives and other data storage devices that have moving mechanical parts.